To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
1. Introduction. The theorem of von Neumann, that every finite, zero-sum two-person game has a value, has been extended in various ways to infinite games. In particular Wald (6) has shown that any bounded game in which one player has finitely many pure strategies, has a value. Our interest was aroused by the infinite analogue of the game of “hide and seek” as described
by von Neumann (5), which does not appear to fit any of the known cases, unless the matrix is bounded.
Von Neumann's fundamental theorem of the theory of games has been extended by various authors and recently in two different directions by Kneser (8) and Nikaidô (9). We present here a form of the theorem, which is more general than that of both these authors. We develop some consequences of this theorem, which make it easier to decide whether certain classes of games have a value and we give several illustrative examples
HIV-positive individuals are at significantly increased risk of depression. In low- and middle-income countries, depression is frequently under-detected, hampered by a lack of data regarding available screening tools. The 5-item World Health Organization Well-Being Index (WHO-5) is widely used to screen for depression, yet its validity in African adults with HIV has yet to be examined.
In this cross-sectional study, we enrolled HIV-positive adults presenting to an outpatient HIV clinic in Mwanza, Tanzania. Patients were administered the Patient Health Questionnaires (PHQ)-2/9 and WHO-5 questionnaires. The rate of positive screens was calculated. Fisher's exact test and Pearson's correlation coefficients between PHQ-2/9 and WHO-5 scores were calculated.
We enrolled 72 HIV-positive adults: rates of positive depression screen were 62.5%, 77.8%, and 47.2% according to PHQ-2, PHQ-9, and WHO-5, respectively. PHQ and WHO results for depression were significantly associated (Fisher's exact test: PHQ-2 v. WHO-5, p = 0.028; PHQ-9 v. WHO-5, p = 0.002). The level of correlation between PHQ and WHO results for depression was moderate (Pearson's correlation coefficient: PHQ-2 v. WHO-5 −0.3289; PHQ-9 v. WHO-5 −0.4463).Per Mantel–Haenszel analysis, screening results were significantly more concordant among patients in the following strata: men, age >40, Sukuma ethnicity, Christian, unmarried, self-employed, at least primary school education completed, and higher than the median income level.
WHO-5 scores correlated well with those of the PHQ-9, suggesting that the WHO-5 represents a valid screening tool. The concordance of PHQ-9 and WHO-5 results was poorer in marginalized socioeconomic groups. Positive depression screens were exceedingly common among HIV-positive Tanzanian adults according to all three questionnaires.
Multi-line data of ammonia (NH3) are presented for Maffei 2, IC 342, and the starburst galaxies NGC 253 and M 82. While in M 82 the NH3 emitting gas is cool, presumably arising from well shielded dense cores deeply embedded in an environment dominated by Photon Dominated Regions, the other galaxies show ‘warm’ and ‘hot’ components that may be heated by shocks, ion-slip or cosmic rays. Interferometric observations show the detailed large scale distribution of NH3 in galaxies for the first time. The first multi-line studies of ammonia at significant redshifts (z = 0.65 and 0.89) are also reported and rotational temperatures, measures of the kinetic temperature of the emitting gas, are derived for all sources.
We report new detections of three H2O megamasers and one kilomaser using the Effelsberg 100-m telescope. Isotropic luminosities are ~50, 300, 1, and 230 L⊙ for Mrk 1066, Mrk 34, NGC 3556, and Arp 299, respectively. Mrk 34 contains the most distant H2O megamaser ever detected in a Seyfert. Our targets in this survey were chosen to fit one of the following criteria: 1) to have a high probability of interaction between the radio jet and the ISM within the central few parsecs of the radio galaxy, yielding masers which arise in local molecular clouds; or 2) to have very bright IRAS sources in which massive star forming regions might yield powerful masers. The ‘jet maser’ sources can provide detailed information about the conditions in the ISM in the central 1-10 pc of AGN. The extra-galactic ‘star formation masers’ can be used to pinpoint and characterize locations of high mass star formation in nearby galaxies. In addition, these sources will help to provide a better understanding of the chemical properties of molecular clouds in extra-galactic systems.
Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.
This study examined high temperature survival and heat shock protein 70 (Hsp70) responses to temperature variation for two marine invertebrate species on sub-Antarctic Marion Island. The isopod Exosphaeroma gigas Leach and the amphipod Hyale hirtipalma Dana had the same tolerance to high temperature. The mean upper temperature which was lethal for 50% of the population (upper lethal temperature, ULT50) was 26.4°C for both species. However, the isopod E. gigas showed significant plasticity of ULT50, with a positive response to acclimation. In addition, the isopod had a heat shock response of Hsp70 at all acclimations, and the amount of Hsp70 protein increased significantly from basal levels upon an acute warm exposure after a cold acclimation. By contrast, the amphipod H. hirtipalma showed limited plasticity of ULT50 and no evidence for a heat shock response (failure of three different Hsp70 antibodies to bind to the extracted 70kDa proteins). Overall, these results reflect different flexibility of thermal tolerance of intertidal invertebrate species on Marion Island, with possible variation in the underlying cellular mechanisms, suggesting that warming associated with climate change may result in changes in species assemblage structure in sub-polar environments.
During the course of some work on the Parmenides, I found I was coming to a conclusion about the First Part of the dialogue which was at variance with what I supposed to be the traditional and commonly accepted view. It therefore seemed advisable to ascertain precisely what this traditional view was, and what were the arguments in favour of it; and the contents of this paper represent some part of an attempt to do this. As it happens, they also tend to make the writer appear as one playing the part of a Zeno to his own Parmenides, showing that even stranger results follow from the hypotheses of those from whom he differs than from his own.
Ash-free-dry-weight determinations for a representative range of living brachiopod genera have revealed that a consistently high proportion of total organic mass is contained within the shell, partly as the organic matrix for biomineralisation and partly as minute extensions of the mantle tissues (caeca) housed within hollow endopunctae permeating the shell. On average 40% to 50% of the total organic mass of both articulate and inarticulate brachiopods is situated within the shell. This is true even for a rhynchonellid brachiopod which does not possess endopunctae, but which has a more dense protein matrix in its shell. The effectively hidden constituent of brachiopod tissue mass which is included in this component has often been overlooked, and as a result total metabolic tissue mass has been underestimated. This throws into question some previous interpretations of brachiopod respiratory and metabolic data.
The oxygen consumption rates of several living brachiopods have been measured, and when respiring tissue in caeca in the shell is taken into consideration, it is clear that brachiopod metabolic rates are low when compared with other marine invertebrates (e.g. between 10% and 50% of the oxygen uptake of comparable gastropods and bivalve molluscs held in similar conditions). This low rate cannot be attributed to a slower pumping rate by the brachiopod lophophore, as has been suggested, because the rate of water movement is comparable to that across the bivalve gill.
Nitrogen excretion rates have also been measured for a few living brachiopods, allowing a comparison with rates of oxygen consumption and providing an indication of the metabolic substrates used. These data on oxygen: nitrogen ratios suggest that one Antarctic brachiopod utilises exclusively protein as a metabolic substrate, while a temperate latitude species uses mainly protein during winter but lipids and carbohydrates during summer months. Histological observations, particularly of Terebratulina retusa from temperate waters, show that a specialised tissue layer in the brachiopod outer mantle epithelium proximal to the shell may be the site of storage of the protein that is metabolised during winter, and of carbohydrate mobilised during gonadal development in summer. The caeca have also been suggested as sites of storage of metabolites, and the possible relationships between these areas of mantle are discussed. It seems that the ability to store nutrients in the mantle, combined with flexibility of substrate utilisation and an inherently low metabolic rate, have been important factors in brachiopod evolution.
Strains of Escherichia coli isolated from adult females with symptomatic urinary tract infection were found to possess the following properties significantly more frequently than faecal strains: (i) high K-antigen titre; (ii) haemolysin; (iii) type 1 pili; (iv) mannose-resistant haemagglutination; (v) fermentation of dulcitol and salicin; (vi) O serotype 2, 6 and 75; (vii) H serotype 1. E. coli isolated from urine specimens containing significant numbers of antibody-coated bacteria were richer in these seven properties than strains from urines without detectable antibody-coated bacteria.
The O and H serotypes of E. coli obtained from patients with urinary tract infection in two New Zealand cities were compared with those reported in the world literature and found to be similar.
X-ray CT scans at two different energies of three articulated specimens of Spathelopsis oakvalensis n. sp., a bivalve from the Bluefield Formation of the Mauch Chunk Group (Mississippian, Chesterian) from southeastern West Virginia, permitted observation and description of poorly known internal features of the shell, resulting in a reversal of the shell orientation alleged by past authors and concomitant reassignment of this problematic genus to the palaeotaxodont family Nuculanidae Adams and Adams. Distinctive posterior and anterior gapes in Spathelopsis suggest separation of inhalant and exhalant water streams, a characteristic associated with derived but not primitive palaeotaxodonts.
We report on the discovery of a supermassive binary black-hole (SBBH) system in the radio galaxy 0402+379, with a projected separation between the two black holes of just 7.3 pc. This is the most compact SBBH pair yet imaged by more than two orders of magnitude. These results are based upon multi-frequency imaging using the Very Long Baseline Array (VLBA) which reveal two compact, variable, flat-spectrum, active nuclei within the elliptical host galaxy of 0402+379. Multi-epoch observations from the VLBA also provide constraints on the total mass and dynamics of the system. The two nuclei appear stationary while the jets emanating from the weaker of the two nuclei appear to move out and terminate in bright hot spots. The discovery of this system has implications for the number of compact binary black holes that might be sources of gravitational radiation. The VLBI Imaging and Polarimetry Survey (VIPS) currently underway should discover several more SBBHs.
Reports on Mississippian rostroconchs from the Appalachian basin are rare. Winchell (1871), Herrick (1888, 1890, 1891), Hyde (1953), and Hoare (1990, 2004) discussed taxa from Ohio. These reports concerned pre-Chesterian occurrences with the exception of the Chesterian Bransonia hydei Hoare, 1990 and Oxyprora sp. Hoare (2004) from the Maxville Limestone. Specimens of the new taxon were reported by Busanus (1974) as Conocardium spp. from the Chesterian Reynolds Limestone in northern West Virginia.
The photographs displayed above show the impact, spreading, and boiling history of n-heptane droplets on a stainless steel surface. The impact velocity, Weber number, and initial droplet diameter are constant (values of 1 m/s, 43 and 1.5 mm respectively), and the view is looking down on the surface at an angle of about 30°. The photographs were taken using a spark flash method and the flash duration was 0.5 μs. The dynamic behavior illustrated in the photographs is a consequence of varying the initial surface temperature.
The effect of surface temperature on droplet shape may be seen by reading across any row; the evolution of droplet shape at various temperatures may be seen by reading down any column. An entrapped air bubble can be seen in the drop when the surface temperature is 24°C. At higher temperatures vigorous bubbling, rather like that of a droplet sizzling on a frying pan, is seen (the boiling point of n-heptane is 98°C) but the bubbles disappear as the Leidenfrost temperature of n-heptane (about 200°C) is exceeded because the droplet become levitated above a cushion of its own vapor and does not make direct contact with the surface. The droplet shape is unaffected by surface temperature in the early stage of the impact process (t≤0.8 ms) but is affected by temperature at later time (cf. t≥ 1.6 ms) because of the progressive influence of intermittent solid-liquid contact as temperature is increased.
It has been observed that a liquid jet impinging on a solid surface can produce splashing. High-speed photography has revealed that, with a turbulent jet, splashing is related to the jet surface roughness. To investigate the importance of the jet shape on splashing, perturbations of known frequency or amplitude are imposed on the surface of a smooth laminar jet.
The top picture shows the unperturbed smooth jet as it spreads radially on the solid surface. The varicose deformations imposed on the jet surface alter the flow quite dramatically (center picture). As we further increase the amplitude of the oscillations, splashing starts suddenly. The bottom picture shows the beauty and complexity of splashing.
Impacting water drops
The four photographs shown here are representative of a series which recorded the structure and evolution of the vorticity generated by a water drop impacting a free surface of water in a container. The 2.8 mm diam water drop was dyed with fluorescein and released from the tip of a hypodermic needle under specific parameters, We=26, Fr=25. The Weber number (ρU2d /γ) and Froude number (U2/gd) are based on drop diameter d, impact velocity U, and surface tension γ.
Figure 1 is photographed from the side and slightly below the free surface while Fig. 2 is shot looking directly up at the free surface via a mirror. These alternative viewing angles provide a valuable tool in visualizing the threedimensional flow structure. A “primary” vortex ring can be seen convecting away from the free surface. A convoluted secondary structure can be seen wrapped around the primary core.